British Prime Minister Boris Johnson failed to convince EU leaders on Monday he has a serious plan for a Brexit deal, then ducked out of a planned news conference under a chorus of abuse from protesters.

Before setting off for talks in Luxembourg, Johnson had compared himself to comic book giant Hulk, but when anti-Brexit protesters gathered he left Prime Minister Xavier Bettel to field questions solo.

A visibly angry Bettel pointed in bitter amusement at the empty podium in front of the British flag beside him as he warned that Britain had failed to come up with any credible way to revive the Brexit withdrawal deal, telling the absent Johnson it was time to ‘stop speaking and act’.

‘For me I have just one withdrawal agreement on the table and it's the one from last year,’ Bettel said. ‘There are no changes, there are no concrete proposals for the moment on the table and I won't give an agreement to ideas.’

After the brief talks with Johnson, Bettel was due to head to Paris for talks with France's President Emmanuel Macron, and he warned EU leaders will not postpone Brexit beyond October 31 if Britain does not come up with written suggestions soon.

‘An extension is only an option it if serves a purpose,’ he warned.

For his part, once he was safely clear of the small crowd of British residents of Luxembourg who had gathered outside Bettel's office for the noisy protest, Johnson made brief remarks to British broadcasters.

‘There was clearly going to be a lot of noise... and I think our points might have been drowned out,’ he protested, insisting he will never seek to postpone Brexit anyway and that he had made progress in agreeing to further talks with EU leader Jean-Claude Juncker and negotiator Michel Barnier.

But Juncker, who had held a working lunch with Johnson, was downbeat.

The president of the European Commission said that once again the UK had failed to come up with a viable alternative to the so-called Irish ‘backstop’ border arrangement.

‘President Juncker recalled that it is the UK's responsibility to come forward with legally operational solutions that are compatible with the Withdrawal Agreement,’ a statement said.

Johnson has vowed to take Britain out of the bloc by the scheduled date of October 31, though parliament has ordered him not to do so without striking a deal with Brussels first.

Businesses and opponents of Brexit say leaving without a deal will cause economic chaos as Britain ends its open trade ties to the European Union after 46 years.

- 'No reason for optimism' -

Johnson says Britain will not agree to a divorce deal that includes the backstop, a provision that would temporarily keep the UK in the EU customs union to keep the Irish border open.

He says he will not delay Brexit beyond October 31 even if it means leaving with no deal.

Before the talks, a UK spokesman stressed London's view that progress was being made in talks between officials to try to find a backstop alternative, but this note of optimism finds no echo in European capitals.

Finland's European affairs minister, Tytti Tuppurainen, who was chairing an EU ministerial meeting in Brussels, said: ‘The European Union is always ready to negotiate when a proper proposal from the UK side is presented.

‘So far I haven't seen any proposal that would compensate the backstop.’

The European Parliament will this week vote on a resolution rejecting Johnson's demand that the backstop clause be stripped from the deal.

Johnson insists it has to be removed if he is to bring the agreement back to the House of Commons for approval.

But the accord will also have to win the support of the other 27 EU leaders and the European Parliament if Britain is not to crash out with no deal on October 31.

Johnson has said he would rather be ‘dead in a ditch’ than ask his European counterparts to postpone Brexit for a third time.

Barnier will address the European Parliament session in Strasbourg on Wednesday as MEPs vote to reaffirm and reinforce the EU Brexit stance -- and insist that the backstop must stay.